LEDs are used in a variety of applications, such as displays, illumination in control panels, in traffic lights and electronic devices. An LED is a semiconductor device that converts electrical energy into optical energy. This occurs when a forward bias is applied to the device, resulting in holes in the P-type semiconductor material combining with the electrons in the N-type semiconductor material at the P-N junction. A “white” light emitting diode uses a blue light emitting diode as the source of the light. A luminous material layered over the blue light emitting diode acts to partly absorb the blue light and convert it into yellow or yellowish green light. When mixed, the blue and yellow/yellowish green light combine as white light.
A conventional method of producing white light emitting devices includes a process in which yttrium aluminate (“YAG”) is directly deposited onto a light emitting diode (“LED”) chip surface in order to produce LEDs that emit white light. However, a disadvantage of said process, and the resulting LED, is that the color temperature from such a white LED is not uniform over a plurality of angular positions due to the non-uniform thickness of the YAG over the LED chip surface. Further, this unequal distribution of color temperature occurs on a device by device basis within the same lot.
In addition, at elevated drive current, bleed-through of radiation in the ultra-violet (“UV”) range can occur. The use of the conventional process in producing these “white” light emitting devices disadvantageously results in package complexity, leading to limited ruggedness and decreased reliability of the devices.